Deliming,bating or pickling with solution containing dimethylsulfoxide



Feb. 25, 1969 w. J. LANGLEY 3,429,548 DELIMING, EATING OR PICKLTNG WITH SOLUTION CONTAINING DIMETHYLSULFOXIDE Filed Aug. 30, 1965 RAWHIDES AND SKINS WASHING LIMING UNHAIRING) BATING AND DELIMING I TANNING FATLIQUORING I PASTING AND DRYING MULLING STACKING REDRYING ILEATHER I WILLIAM J. LANGLEY INVENTOR.

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ATTORNEY United States Patent 3 Claims This invention relates to the manufacture of leather and more particularly, to an improved process of converting hides and skins to leather and to the leather produced thereby. The terms hides and skins include all animal hides and skins that are converted to leather comcercially. In the process of converting hides and skins to leather, the hides and skins are subjected to a number of operations in carrying out the conversion process. Each operation is designed to secure a particular effect or object in affecting the conversion to leather. Such operations and the objects thereof include the following:

SOAKING AND WASHING This operation has two purposes. The first is to wash from the stock the water soluble material that might otherwise cause difiiculties in later operations, and the second is to cause the fibers to absorb water to restore them to their natural or normal sizes and shapes.

LIMING (UNHAIRING) The purpose of this operation is to free the hides and skins from hair and epidermis and from the glands of the thermostat layer.

DELIMING AND BATING This operation has two purposes. The first is to reduce the pH and the second is to digest certain undesirable constituents such as degredation products of the epidermal system and fibers which provide structural support in the grain layer.

PICKLlNG Saturating unhaired hides and skins with a solution of acid and salt to further reduce the pH, and prepare them for tanning.

TANNING The treatment of hides and skins chemically to make them permanently more resistant to decomposition.

COLORING The drum-dyeing of leather to impart the desired color to the leather.

FATLIQUORING The application of oils to leather in the form of emulsions in water to reduce hardness and stiffness and provide softness and flexibility.

DRYING (PASTING OR TOGGLING) Stretching out a piece of damp leather and holding it in place for drying in a smooth and stretched condition by paste or toggles.

MULLING (OR SAMMING) 3,429,648 Patented Feb. 25, 1969 desirable and of considerable advantage and use to the leather manufacturing industry to be able to convert hides and skins to leather at greatly reduced times of processing, together with a reduction in the amount of processing chemicals involved while at the same time providing a leather product of improved quality.

Accordingly, a principal object of the present invention is to provide an improved process for manufacturing leather from hides and skins so as to produce highquality leather at reduced processing times.

Another object of the present invention is to provide a more economic process of converting hides and skins to leather products of improved quality and uniformity.

Another object of the present invention is to provide an improved process for converting hides and skins to leather which does not require the installation of special processing equipment by the manufacturer or tanner.

Still another object of the present invention is to provide a process of the above type which does not require substantial deviation from the use of regular or standard processing chemicals; and which does not disrupt the continuity of normal production routine.

Other objects of the invention will in part be obvious and will in part appear hereinafter.

The invention accordingly comprises the process involving the several steps and the relation and the order of one or more of such steps, with respect to each of the others and the product possessing the features, elements and arrangement of parts which are exemplified in the following detailed disclosure, and the scope of the application of which will be indicated in the claims.

For a fuller understanding of the nature and objects of the invention, reference should be had to the following detailed description, taken in connection with the accompanying drawing which is a diagrammatic flow sheet illustrating one embodiment of the invention.

In accordance with the present invention, the above objects are achieved by employing a composition for the various conversion operations which comprises dimethylsulfoxide and a solvent for the dimethylsulfoxide.

It has been found that a solvent selected from the group consisting of water and alcohol is suitable. As an alcohol, both monohydric and polyhydric alcohols, such as ethyl alcohol, butyl alcohol, isopropyl alcohol, and propylene glycol are suitable. Additionally, one or more alcohols may be used together. One important feature of the solvent is that the water and the alcohol when used singly or together as a solvent, reduce the melting point or freezing point of the dimethylsulfoxide thereby permitting the dimethylsulfoxide to remain in solution and provide for a more uniform action.

Where the composition is to be used in a nonaqueous medium, the composition preferably includes water. In this case the water serves to provide a clear uniform solution with uni-form action of the composition. While the amount of water employed is not critical it has been found that about 15% by weight of composition is sufficient to provide a clear solution. It is to be understood that sufiicient water is added until the solution becomes clear.

In accordance with the present invention, the composition consists of between 10% to 50% dimethylsulfoxide, the balance being the solvent. While additional dimethylsulfoxide may be employed up to about it has been found that such additional amounts are not of economic advantage. With respect to the weight of the hides and skins or leather, the dimethylsulfoxide is preferably between about 1% to 10% of such weight. While greater amounts of the dimethylsulfoxide may be employed up to about 13% of the stock weight, such additional amounts are not of economic advantage.

Additionally, if desired, an antifoam agent and a grease dispersing agent may be included in the composition. As an antifoam agent Dow Antifoam A has been found satisfactory although other commercial antifoarn agents are suitable. Preferably between about 0.2% to 2% by weight of the antifoarn agent is suflicient. As a grease dispersant, a commercial dispersant produced by Rohm and Haas and sold under the trade name Triton X-100 is satisfactory although other commercial grease dispersants are suitable. Preferably the composition contains between about 1% to 3% by weight of the grease dispersant as used.

It has been found that the composition of the present invention is applicable to all types of hides and skins regardless of the origin shade, or color, grade, or weights. Equally important is the fact that the composition of the present invention does not require the installation of special processing equipment by the leather manufacturer or tanner, but can be used in the conventional equipment.

Additionally, the leather manufacturer or tanner can employ the composition of the present invention without departing from the use of conventional processing chemicals and without disrupting the continuity of his normal production routine.

It has been found that leathers produced using the compositions of the present invention possess an unprecedented uniformity of temper throughout the entire hide or skin area, as well as an unusually high degree of tensile, grain, and stitch-tear strength. Additionally, leathers produced in accordance with the present invention do not require the addition of preservatives or antioxidants, as the leathers do not spew, oxidize or bloom. Additionally, leathers produced in accordance with the present invention do not stiffen as a result of exposure to low atmospheric temperatures, or as a result of drying after exposure to excessive dampness or wetness. Other advantages of leathers produced in accordance with the present invention are that they possess an unusually tight break, fullness, resilience or bounce; easily controlled fatliquor penetration and desired degree of temper; complete uniformity of color; superior bufling and shaving results; compatibility to all types of finishes; and the capacity of the leather to withstand repeated stakings without the tightness of the break or the grain strength being adversely affected. Resistance to crocking and bleeding of color has also been observed.

The invention will now be described by way of the following nonlimiting examples:

Example 1 In this example the basic raw stock is cattle hide of steer origin, which has been cured by green salting. In this example and the following example, the percentages referred to are based on the green salted weight of the basic raw stock unless otherwise indicated. The raw stock is then subjected to the following operations:

(1) Washing.The raw stock is placed in a conventional drum with 250% of cold tap water and the drum ming procedure started. There is then added to the drum about 2.5% of the composition of the present invention.

The composition as used in this example consists by weight of the following:

Percent (a) Dimethylsulfoxide 50 (b) Isopropyl alcohol (c) Propylene glycol 10 (d) Water l5 Drumming is continued for about five minutes after the addition of the composition. The stock is then drumwashed for ten to fifteen minutes with a constant flow of cold tap water. The stock is then removed, horsed-up to drain for ten to fifteen minutes and cut into sides.

(2) Soaking.In this operation the stock is placed in a conventional soak paddle with 350%-400% tap water and paddling started. The composition in the amount of 10% is added while paddle is in motion and the paddling continued for three to four hours at 65-70 F. The stock is then removed and drained for ten to fifteen minutes and then green-fleshed and trimmed.

(3) Liming (unhairing).ln this operation the stock is floated in a paddle drum with a premixture of the following percentages based on green-fleshed weight:

(a) 300-350% tap water (70-75" F.) (b) 5% hydrated lime, Ca(OI-I) (c) 0.75% sodium sulfide, Na S9H O (d) 10% of the composition The stock is then paddled for about thirty minutes at a temperature of about 70-75 F. The stock is then rested for three hours, paddled for thirty minutes, rested for three hours, paddled for thirty minutes, rested for three hours, paddled for thirty minutes, and then rested for one hour for a total liming time of twelve hours. The pH of the stock as tested is about 12.4-12.6. The stock is then tumbled for about 8 to 10 revolutions, drain paddled and then refloated with 300% to 350% tap water and paddle washed for ten to fifteen minutes. The stock is then pulled and horsed-up to drain for ten to fifteen minutes.

The stock is then subjected to mechanical unhairing by passing the stock through a conventional unhairing machine for complete depil'ation. Following the unhairing process, the stock is subjected to the conventional mechanical fleshing to remove flesh and muscle tissue adhering to the inner or flesh surface of the stock. The stock is then subjected to the conventional mechanical scudding to remove any remaining hair, surface cells and dirt. Following the scudding the stock is then washed with a float of ZOO-250% tap water at 65-70 F. for ten to fifteen minutes, then pulled and horsed-up to drain for five to ten minutes. The stock is then passed through a conventional splitting machine to separate the top grain layer from the split layer.

(4) Eating and deliming.The top grain stock is then placed in a wash drum with ZOO-250% (hereafter percentages, unless otherwise indicated are based on the lime split-weight) tap water at a temperature of about -95 F. and washed for ten to fifteen minutes. The water is then adjusted to about ISO-175% and drum washing started. The following mixture is then added to the drum:

(a) 10% of the composition. (b) 1% of a commercial bating and deliming agent such as Oropon C sold by Rohn & Haas.

The stock is then drummed for one hour while maintaining a drum float temperature of about 90-95 F. The pH of the stock as tested is about 8.2 to 8.8. The stock is then drained and washed with tap water 8590 Ff for ten to fifteen minutes.

(5) Pickling.-The stock is then floated in the same drum with 100-125% tap water at 85-90 F. There is then added 6% sodium chloride salt with five to ten minutes of drumming to dissolve the salt. One percent sulfuric acid is then added followed by drumming for about thirty to forty-five minutes with a drum temperature of about 85-90 F. The pH of the stock is between about 1 to 2.5.

(6) Tanning-To the pickling drum solution of operation 5, the following was added in order:

(a) 10% of the composition followed by drumming for five to ten minutes to assure complete mixture.

(b) 2.5% of basic chromic sulfate is added in a single feed to the stock. A basic chromic sulfate in solution form as produced by Diamond Alkali and sold under the trade name Tanolin R is suitable.

(c) 0.5% of sodium bicarbonate dissolved in 7-8 parts of tap water at about 100 F. is divided into two equal volumes and added in two feeds with about ten minutes of drumming after each addition.

The stock is then drained and washed for five to ten minutes with tap water at a temperature of about -100 F.

The stock is then refloated in the same drum with 100- 125% tap water at 90-95 F. The pH of the stock as tested is between about 3.5 and 4.0.

(7) Retanning.-To the water in the drum of operation 6, the following is added:

(a) 1.25% of neutral to alkaline commercial Syntan, a sulfonated condensate of napthalene and formaldehyde, is used in this step of the operation. A commercial syntau sold under the trade name Tamol N and produced by Rohm & Haas is suitable. The syntan is dissolved in 7-8 parts of tap water of about 100 F. and then added to the drum in a single feed. The drum is then run for about fifteen minutes at a temperature of about 90-95 F.

( b) 2% eucalyptus liquid extract with 1% Commercial Gambier liquid extract are mixed with 2 to 3 parts tap water and then added to the drum.

The drum is then run for fifteen to twenty minutes at 90-95 F. and then drained. The stock is then washed with tap water at 95-100 F. for five to ten minutes, then pulled and horsed-up to drain for five to ten minutes. The pH of the stock is between 3.5 and 4.5.

(8) Coloring.After setting-out and shaving by machine in the conventional manner well-known in the art, the tan-shaved stock is floated in the drum with 100-125% water (hereafter, unless otherwise indicated, percentages are based on the shaved weight of the stock), and washed for five to ten minutes. The Water is then adjusted to 100% and drumming started. There is then added of the composition. After about five minutes of drumming at a temperature of about 120 F. to 125 F. there is then added 4% of a commercial red acid dyestuif dissolved in 6-7 parts of water. After about five minutes of drumming, of Neovadine AN, a dyeing (leveling) assist, produced by Ciba Chemical & Dyestuffs Company, in 3 or 4 parts of water, is added and the drumming continued for about ten minutes.

(9) Fatliquoring.The stock is then subjected to the process known as fatliquoring by the addition of 2% of a multicharged fatliquor oil consisting of a blend of sperm oil and neatsfood oil in 4 or 5 parts of water. Drumming is continued for ten to fifteen minutes at a temperature of 120-125 F. The stock is then drained in the wheel, and horsed-up to drain for ten to fifteen minutes.

l0) Pasting and drying-The stock is then pasted and dried in the conventional manner. The drying time is approximately two hours.

(11) Mulling, staking, and redrying.The stock in sequence is then mulled, staked, and redried in the conventional manner. Mulling is carried out for twenty-four hours. Redrying of the stock is carried out for sixty minutes.

Example 2 In this example, the raw stock is cattle hide of steer origin and cured by green-salting similar to Example 1. The stock is processed through the same operational steps (1 through 11) as in Example 1, with the exception that the additions of the compositions of the present invention are omitted. For simplicity only the differences between this example and Example 1 will be mentioned. Example 2 thus illustrates a conventional process used by manufacturers or tanners for converting hides and skins to leather.

(1) Washing.The stock is drum-washed for about forty-five minutes. The stock is then horsed-up to drain for about forty-five minutes.

(2) Soaking-The floated stock is paddled for about five minutes and then soaked for from twenty-four to thirty-six hours. The stock is drained for from forty-five to sixty minutes.

(3) Lirning.The premixture contains 7% hydrated lime and 1.25% sodium sulfide. The stock is soaked in the solution for twenty-four to thirty-six hours with periodic paddling for five to ten minutes every three to four hours. The stock is drained in each instance for one to one and one-half hours. Following the scudding, the stock is washed for about twenty-five minutes and then drained for one to one and onehalf hours prior to splitting.

(4) Rating and deliming-The top grain stock is washed for a period of about twenty-five minutes at a temperature of -90 F. The mixture contains 2% of the deliming agent, Oropon C. The stock is drummed for about three hours.

(5) Pickling.8.0% sodium chloride and 2% sulfuric acid are added followed by drumming for about three hours.

(6) Tanning-The drum is drained and the stock washed for fifteen to twenty minutes with tap water at a temperature of about 85-90 F. The stock is then refloated in the same drum wheel with 100-125 tap water at 85-90 F. To the drum is then added 8-9% basic chromic sulfate. The basic chromic sulfate is added in three equal parts, the feeds being added at intervals of about thirty minutes. The drum is run for four hours after the addition of the last feed. The drum is then drained and the stock washed for ten to fifteen minutes with tap water at -100 F. The stock is then refloated with 125% tap water. 2% of sodium bicarbonate is added in three equal feeds at fifteen minute intervals. 4 /z% of syntan is added and the stock drummed for about twentyfive minutes. 4% eucalyptus extract and 2% Gambier extract are used. The stock is drummed for one hour at 95-100 F.; Washed for twenty minutes at 95-100 F. and horsed-up to drain for about one and one-half hours.

(7) Coloring-6% of the dyestuff is used. /2% of the Neovadine AN is used, followed by drumming for about thirty minutes. Thereafter, 3% formic acid in two equal feeds at an interval of fifteen minutes and a temperature of -130" F. The drum is then drained, the stock washed for twenty minutes with tap water at 120-125" F. and then refloated with 100% water at l20-l25 F.

(8) Fatliquoring.-Thereafter, 4 /2 of a stufilng filler type fatliquor of 90% activity based on animal and fish oils, and an organic filler is added. After drumming for twenty minutes there is added a blend of 4% of a sperm and vegetable oil-based fatliquor of 70-75% activity having a sulfurtrioxide content of 56%; and 3% of a straight sperm oil fatliquor of 70-75% activity and sulfur trioxide content of 8-9%. The stock is drummed for forty minutes at 120-125 F. and then removed, horsed-up and drained for about one hour.

(9) Pasting and drying-The drying time is approximately four hours. a

(10) Mulling, stacking and redrying-The mulling is carried out for five days and redrying for approximately two hours.

The leather produced in accordance with the present invention, as illustrated by Example 1, possesses vastly improved qualities mentioned above including uniformity of temper, color and density of fibers; and an unexpected high degree of tensile, grain and stitch-tear strength, when compared to the leather produced in Example 2, which illustrates a conventional commercial process of converting hides and skins to leather. Additionally, Example 1 illustrates that the process of the present invention provides for a reduction in processing time and chemicals used. These latter features of the present invention are believed to be clearly illustrated by reference to the table which sets forth the average reduction of time and chemicals as a function of amount of the composition of the present invention employed; the table being based on results of various types, grades, weights and tannages of leather processed in accordance with the present invention.

As can be seen from the table, the compositions of the present invention, when employed in operations from soaking through redrying in amounts ranging from 5 to 13%, provide for reductions of from 45% to 90% of the time normally required to complete the particular operations in the conversions of hides and skins to leather. The drying time, for example, is reduced from to without adversely aflFecting the lubricity of the stock. Also, the compositions of the present invention allow significant reduction in the amount of processing chemicals involved while at the same time providing leathers of overall superior quality. The most Significant of the reduction of processing chemicals are the deliming and bating, tanning, retanning, coloring and fatliquoring operations; particularly the fatliquoring, where the amount of fatliquor ordinarily employed may be reduced by from 50% to Additionally, the amount of tanning agent, whether vegetable, mineral, or synthetic organic, may be reduced by from 20% to 30%.

TABLE Percent composition Operation (containing 50% di- Percent Percent methylsu1toxide 50% reduction reduction solvent) of time of chemicals Soaking 5 green-salted weight 10 green-salted weight- 15 green-salted weight. Washing 5 green-salted weight. 10 green-salted weight. l5 green-salted weight. Liming (unhairing) 5 green-salted weight.

10 green-salted weight- 15 green-salted weight- Deliming and hating- 5 lime split weight 10 lime split weight- 15 lime split weight- Pickling 5 as retained Tanning Retanning Coloring Fatliquoring 5 shaved weight 10 shaved weight 15 shaved weight Drying 5 as retained" 10 as retained. 15 as retained- Mulling 5 as retained 10 as retained 15 as retained- Redrying 5 as retained 10 as retained- 15 as retained.

As retained amount of composition retained from prior operation.

Since certain changes may be made in the above process and composition without departing from the scope of the invention herein involved, it is intended that all matter contained in the above description or shown in the accompanying drawing, shall be interpreted as illustrative and not in a limiting sense.

What is claimed is:

1. In the process of hating and deliming hides and skins the step which comprises immersing them in an aqueous solution of a bating and deliming agent to which has been added dimethylsulfoxide.

2. In the process of hating and deliming hides and skins the step which comprises contacting them with an aqueous solution of a commercial bating and deliming agent containing 1% to 13%, based on lime split weight, of a composition comprising 10% to by weight dimethylsulfoxide, and up to 50% by weight of an alcohol selected from the group consisting of monohydric and polyhydric alcohols.

3. The process of pickling hides and skins comprising the steps of impregnating the hides and skins with a composition comprising 1% to 13% dimethylsulfoxide, up to 5% alcohol, the balance being Water, said percents being based on the lime split weight of the hides and skins, draining the hides and skins, thereafter contacting the hides and skins with an aqueous salt solution for a period of less than about an hour, adding acid to said salt solution, and removing the hides and skins after they have been in contact with the resultant solution for about 1 to 2 hours.

References Cited UNITED STATES PATENTS 2,365,898 12/1944 Morris et al. 19613 2,942,008 6/ 1960 Lubowe 252364 2,993,794 7/ 1961 Moshy 9918 3,023,183 2/ 1962 Nelson 260-302 3,007,763 11/1961 Adams 894.33 XR 3,120,423 2/ 1964 Herschler et a1. 855 3,279,881 10/1966 Anderson 894.32

I. TRAVIS BROWN, Primary Examiner.

DONALD LEVY, Assistant Examiner.

US Cl. X.R. 

1. IN THE PROCESS OF BATING AND DELIMING HIDES AND SKINS THE STEP WHICH COMPRISES IMMERSIN THEM IN AN 